# 125 CI flange and 150 CI Flange

[GasProcess]

We have to replace 125# FF ductile iron / C.I. valves ( material - A536 65-45-12 & A126 GrB / A126 Gr B ) with the existing 150# RF valves. The flange on the water filter where the valve is installed is #150 RF. There is spacer installed at present between the valve and the vessel flange.

Is it possible to fabricate a spacer flange from 150# Blind flange so that the RF of the bling flange mates with the vessel and the FF of the blind flange mates with the 125# FF flange of the valve. By using a full face gasket will a leak proof joint will be ensured?

Also any tips on gasket material selection would be greatly appriciated

 

[pipingdesigner]

Ahh, this old chestnut.

This has come up before on this forum and this is what I posted:

Flat Face (FF) - The Flat Face is primarily used on Cast Iron flanges. With this face the whole contact face of the flange is machined flat.

Raised Face (RF) - The Raised Face is most common of all flange faces. The flange has a raised area machined on the flange face equal to the contact area of a gasket.

Flat face flanges are never to be bolted to a raised face flange. If you need to bolt a Forged steel flange to cast iron then you must call for the forged steel flange to be machined off to a flat face.

For more information on flanges, flange faces, gaskets and bolting see

http://www.pipingdesigners.com/Training - section 1d.htm

The link to the original posting, with other points of view is below:

http://www.eng-tips.com/viewthread.cfm?qid=153573&page=7

Hope it helps

pipingdesigner

http://www.pipingdesigners.com

 

[GasProcess]

Piping designer

This is what we are proposing to do. By inserting a blind flange spacer it will be FF against the FF C.I. Flange and RF face against RF flange.

My questing is if it is going to be leak proof and any additional staring on gasket etc